pentimento

pentimento (pĕnˌtəmĕnˈtō) [key], painter's term for the evidence in a work that the original composition has been changed. Often the opaque pigment with which the artist covered a mistake or unwanted beginnings will, with time or injudicious cleaning, become transparent, and a revelation of original intentions will become visible through the finished composition. A celebrated example is Caravaggio's Lute Player (Metropolitan Museum of Art) in which X-ray photography was used to uncover evidence of the painter's original intention.